The subject invention relates to vehicular exhaust mufflers having an outer shell surrounding a stamp formed internal assembly and end caps and inlet and exhaust tubes at opposed ends of the outer shell. More particularly, the subject invention is directed to an improved stamp formed internal assembly for decreasing manufacturing costs and increasing the muffler useful life.
Vehicular mufflers are today very commonly constructed using stamp formed sheet metal outer shells as well as internal assemblies. The internal assemblies quite often incorporate and form baffles, exhaust tubes and other components utilized in attenuating and decreasing the apparent sound generated by the vehicle engine. By stamp forming, the various muffler component parts manufacturing costs can be significantly decreased. Several such mufflers which have been constructed using various stamp formed component parts are, for example, shown and described in Gerber, U.S. Pat. No. 5,816,361, Gerber et al., U.S. Pat. No. 5,717,173, Wilcox, et al., U.S. Pat. No. 4,941,545 and Wolfhugel, U.S. Pat. No. 4,396,090.
The Gerber, U.S. Pat. No. 5,816,361, for example, discloses a muffler constructed with a tubular outer shell and end caps attached thereto at each end thereof An internal cartridge or assembly is provided and constructed of stamp formed component parts. These assemblies or cartridges are constructed using two identical stamp formed plates which have been placed in mirror relation with respect to one another forming baffles at each end thereof and tubes extending therebetween. Each of the tubes include perforations. Although this muffler and the stamp formed assembly therein provide for a generally inexpensive means of manufacturing, it has shortcoming and drawbacks. For example, the stamp formed plates are assembled by spot welding and, as a consequence, the coating of the sheet metal as well as the sheet metal itself is weakened thereat thereby causing premature deterioration thereof by the acidic water which typically condenses within the muffler. Additionally, this condensate of acidic water is not readily removed from the central chambers between the baffles causing accumulation thereof and furthering premature deterioration of the stamp formed plates and assembly. Further yet, most prior mufflers tend to be limited in their application to only certain vehicles or with only certain exhaust engines.
Accordingly, a need exists for a muffler constructed using stamp formed sheet metal component parts which decreases manufacturing costs and which is more resistant to deterioration and which is, further, more universal for use on different vehicles and exhaust engines.
It is the principal object of the present invention to overcome the above-discussed disadvantages associated with prior mufflers constructed using stamp formed sheet metal components. The present invention overcomes the disadvantages associated with prior mufflers by providing a muffler having a tubular outer shell and end caps connected to opposed ends thereof. A pair of stampings or stamp formed sheet metal plates are connected to each other in a face to face relationship and forming an assembly which includes a least three tubes extending between baffles. The sheet metal stampings are identical to one another and are also located in mirror image relation with respect to one another for forming the assembly. The assembly is received within the muffler outer shell and an inlet tube extends through one of the end caps and communicates with one of the assembly tubes. At the other end of the muffler, an outlet tube extends through that end cap and communicates with another one of the assembly tubes. As constructed, the assembly baffles divide the volume within the outer shell for providing a first chamber between the muffler inlet end and a baffle, a second chamber between the outlet end and the other baffle and a central chamber between the baffles. Preferably, the stampings portions forming the assembly between the baffles extend to the inner surface of the outer shell thereby dividing the central chamber into upper and lower central chambers.
Each of the stampings or plates include baffle portions at opposing ends and further include valley portions and semicircular portions extending longitudinally between the baffle end portions. The valley portions are located between the semicircular portions so that, when the stampings are located in mirror image relation and face to face to one another with the valley portions of one stamping located adjacent the valley portion of the other stamping and the semicircular portions of one stamping located adjacent the semicircular portions of the other stamping, the resultant assembly includes longitudinally extending tubes formed by the semicircular portions extending between the end baffle portions.
The sheet metal stampings or plates are attached to one another by rivets which are provided at the valley portions of the stampings. Preferably, the stampings are provided with alternating rivet holes and annular protrusions in each of the stamping valley portions such that, when two stampings are placed in mirror image relation with respect to one another and face to face, the annular protrusions of one stamping are received within the rivet holes of the other stamping. After the stampings are place in mirror image relation with respect to one another and with the annular protrusions of one of the stampings extending through the rivet holes of the other stamping, the annular protrusions are deformed radially outwardly thereby clamping or fixedly attaching the stampings together thereat. With this rivet type attachment, the protective coating of the sheet metal is not damaged or otherwise compromised except for the cut surfaces of the rivet holes and annular protrusions. Additionally, the deforming or bending over of the sheet metal over the rivet holes further reinforces the attachment providing additional mass unlike, for example, spot welding.
So as to further decrease deterioration of the stampings and increase the life of the muffler, each of the baffles are provided with an impression whereby, upon insertion of the assembly within the outer shell and locating the baffles therein, the impressions form weep holes between the upper and lower chambers and the first and second chambers. Thus, the acidic water which condenses within the upper and lower central chambers readily and easily exits through these weep holes and to the first or second chambers wherefrom the water can be expelled through a hole provided in the muffler outer shell or end cap. By only providing an impression along the outer edge of the stamping portion which forms the baffle, the sheet metal coating is again not removed or otherwise compromised thereby preventing rapid deterioration thereof and lengthening the life of the muffler.
The muffler is further improved by providing a design which is substantially more universal and usable on different vehicles and exhaust engines. In this regard, each of the assembly tubes are provided with one or more rows of openings for providing communication between the assembly tubes and the upper and lower central chambers. The openings are louver shaped and, preferably, one-half of the row of louvers open longitudinally generally toward the inlet end of the muffler and the other one-half of the row of louvers open generally longitudinally in the opposite direction toward the exhaust end of the muffler. It has been found that, most preferably, two rows of louvers identical to the first and wherein each row includes ten louver shaped openings, five of which open in the direction of the inlet end and the other five opening in appositive direction toward the exhaust end, advantageously cause exhaust noise to be attenuated in the upper and lower central chambers for many different vehicles and exhaust engines. Yet more preferably, each of the two rows of louver shaped openings are located on each stamping semicircular portion less than forty-five degrees radially from each other around the semicircular portion which forms the assembly tubes.
In one form thereof, the present invention is directed to a muffler including a outer shell having an inlet end and an exhaust end. A pair of stampings are provided and form an assembly which includes a least three tubes extending between baffles. The assembly is received within the outer shell and therewith forms a first chamber between the inlet end and a baffle, a second chamber between the outlet end and a baffle and a central chamber between the baffles. An inlet tube extends through the inlet end and communicates with one of the assembly tubes. An outlet tube extends through the outlet end and communicates with another one of the assembly tubes. A plurality of openings are provided between at least one of the assembly tubes and the central chamber. The stampings are provided with an impression for thereby forming weep holes between the central chamber and the first and second chambers whereby water may travel between the central chamber and the first and second chambers. The assembly tube openings are louver shaped. Each of the stampings are identical to one another and include valley portions between semicircular portions. The stampings are located in mirror image relation with respect to one another with the valley portions of one stamping located adjacent the valley portions of another stamping and the semicircular portions of one stamping located adjacent to the semicircular portions of the other stamping thereby forming the assembly. A rivet assembly is provided at the valley portions for retaining the stampings together.